A reverse engineering system for rapid manufacturing of complex objects

This paper presents a reverse engineering system for rapid modeling and manufacturing of products with complex surfaces. The system consists of three main components: a 3D optical digitizing system, a surface reconstruction software and a rapid prototyping machine. The unique features of the 3D optical digitizing system include the use of white-light source, and cost-effective and quick image acquisition. The surface reconstruction process consists of three major steps: (1) range view registration by an iterative closed-form solution, (2) range surface integration by reconstructing an implicit function to update the volumetric grid, and (3) iso-surface extraction by the Marching Cubes algorithm. The modeling software exports models in STL format, which are used as input to an FDM 2000 machine to manufacture products. The examples are included to illustrate the systems and the methods.     

Three-dimensional optical measurements and reverse engineering for automotive applications

The paper describes a very special and suggestive example of optical three-dimensional (3D) acquisition, reverse engineering and rapid prototyping of a historic automobile, a Ferrari 250 Mille Miglia, performed primarily using an optical 3D whole-field digitiser based on the projection of incoherent light (OPL-3D, developed in our laboratory). The entire process consists in the acquisition, the point cloud alignment, the triangle model definition, the NURBS creation, the production of the STL file, and finally the generation of a scaled replica of the car.The process, apart from the importance of the application to a unique, prestigious historic racing car, demonstrates the ease of application of the optical system to the gauging and the reverse engineering of large surfaces, as automobile body press parts and full-size clays, with high accuracy and reduced processing time, for design and restyling applications.     

Impact of CAD tools on creative problem solving in engineering design

This paper presents the results of a survey of CAD users that examined the ways in which their computational environment may influence their ability to design creatively. This extensive online survey builds upon the findings of an earlier observational case study of the use of computer tools by a small engineering team. The case study was conducted during the conceptual and detailed stages of the design of a first-to-world product. Four mechanisms by which CAD tools may influence the creative problem solving process were investigated: enhanced visualisation and communication, circumscribed thinking, premature design fixation and bounded ideation. The prevalence of these mechanisms was examined via a series of questions that probed the user’s mode of working, attitudes, and responses to hypothetical situations. The survey showed good support for the first three mechanisms and moderate support for the fourth. The results have important implications for both the users and designers of CAD tools.     

An integrated manufacturing system for rapid tooling based on rapid prototyping

To reduce the time and cost of moulds fabrication, a novel integrated developing and manufacturing system of rapid tooling (RT) based on rapid prototyping (RP) is proposed. The architecture of system which consists of four building blocks: digital prototype, virtual prototype (VP), physical prototype and RT system, is presented. A digital prototype can be established by 3D CAD software packages or reveres engineering technique. A VP is employed to guide in optimization of the mould design and manufacturing process planning. A physical prototype, which is built using RP technology, generally serves as a pattern for producing RT. By integrating these building blocks closely, the system can aid effectively in mould design, analysis, prototyping, simulating, and manufacturing process development. Three typical cases are discussed in detail to illustrate the application of the system. It has been shown from a number of case studies that the system has a high potential to reduce further the cycle and cost of die development while minimizing error introduction. As a result, the integrated system provides a feasible and useful tool for companies to speed up their product development.     

Adapting paper prototyping for designing user interfaces for multiple display environments

A multiple display environment (MDE) networks personal and shared devices to form a virtual workspace, and designers are just beginning to grapple with the challenges of developing interfaces tailored for these environments. To develop effective interfaces for MDEs, designers must employ methods that allow them to rapidly generate and test alternative designs early in the design process. Paper prototyping offers one promising method, but needs to be adapted to effectively simulate the use of multiple displays and allow testing with groups of users. In this paper, we share experiences from two projects in which paper prototyping was utilized to explore interfaces for MDEs. We identify problems encountered when applying the traditional method, describe how these problems were overcome, and distill our experiences into recommendations that others can draw upon. By following our recommendations, designers need only make minor modifications to the existing method to better realize benefits of paper prototyping for MDEs.     

Rapid prototyping technology: applications and benefits for rapid product development

In recent years, rapid prototyping technology (RPT) has been implemented in many spheres of industry, particularly in the area of product development. Existing processes provide the capability to rapidly produce a tangible solid part, directly from three dimensional CAD data from a range of materials such as photocurable resin, powders and paper. This paper gives an overview of the growth and trend of the technology, areas of applications and its significant benefits to manufacturing industries.     

A process for solvent welded rapid prototype tooling

Rapid prototyping is widely seen as an effective tool for compressing time to market for new products. The typical process followed by industrial and mechanical design groups is to model a new product in a CAD system, rapidly prototype the component parts, use the parts as patterns for RTV silicone molds, and then cast polyurethane prototype parts from the molds. These prototype components are an integral part of the simultaneous engineering process. With prototype components, engineers are able to design, implement, test, and refine the assembly systems for a product while production tooling for the components is being made. In this paper, we describe an experimental rapid prototyping process, known as solvent welding freeform fabrication (SWIFT), that is very well suited to the production of short to medium run tooling. The advantage of the process is that it is very fast and inexpensive relative to the traditional RTV silicone mold making process. The process also produces ABS or polystyrene molds which last considerably longer than RTV silicone molds. Process development details are provided in the paper and its application to a power tool component is described.     

基于Windows的快速成形实时控制系统

分析了光固化快速成形机控制系统功能需求，设计了单机型快速成形机的控制系统，并且详细介绍了控制系统的总体结构及其特点。对于基于Windows的控制系统实时性进行了详细的论述，由于Windows系统在中断处理、线程调度和内核可被抢先等的特点，该文通过设计定时器的虚拟设备驱动程序和提高线程的优先级的方法，达到了控制系统的实时性能。     

Adaptive tool-path generation of rapid prototyping for complex product models

Rapid prototyping (RP) provides an effective method for model verification and product development collaboration. A challenging research issue in RP is how to shorten the build time and improve the surface accuracy especially for complex product models. In this paper, systematic adaptive algorithms and strategies have been developed to address the challenge. A slicing algorithm has been first developed for directly slicing a Computer-Aided Design (CAD) model as a number of RP layers. Closed Non-Uniform Rational B-Spline (NURBS) curves have been introduced to represent the contours of the layers to maintain the surface accuracy of the CAD model. Based on it, a mixed and adaptive tool-path generation algorithm, which is aimed to optimize both the surface quality and fabrication efficiency in RP, has been then developed. The algorithm can generate contour tool-paths for the boundary of each RP sliced layer to reduce the surface errors of the model, and zigzag tool-paths for the internal area of the layer to speed up fabrication. In addition, based on developed build time analysis mathematical models, adaptive strategies have been devised to generate variable speeds for contour tool-paths to address the geometric characteristics in each layer to reduce build time, and to identify the best slope degree of zigzag tool-paths to further minimize the build time. In the end, case studies of complex product models have been used to validate and showcase the performance of the developed algorithms in terms of processing effectiveness and surface accuracy.     

Curve interpolation with directional constraints for engineering design

An algorithm to interpolate data points with directional constraints is given in this paper. The interpolating B-spline curve passes through the data points and assumes tangent directions at arbitrarily selected points. The advantages of the method is that the user is free to select any number of directional constraints and the method produces full parametric continuity up to C ^{p − 1} for any degree p interpolation. The method is a generalization of Piegl and Tiller (The NURBS book, 2nd edn. Springer, New York, 1997] in two directions: (1) there is no restriction on the degree, and (2) no need to specify derivatives at all data points.     

Hybrid-Game Strategies for multi-objective design optimization in engineering

A number of Game Strategies (GS) have been developed in past decades. They have been used in the fields of economics, engineering, computer science and biology due to their efficiency in solving design optimization problems. In addition, research in multi-objective (MO) and multidisciplinary design optimization (MDO) has focused on developing robust and efficient optimization methods to produce a set of high quality solutions with low computational cost. In this paper, two optimization techniques are considered; the first optimization method uses multi-fidelity hierarchical Pareto optimality. The second optimization method uses the combination of two Game Strategies; Nash-equilibrium and Pareto optimality. The paper shows how Game Strategies can be hybridised and coupled to Multi-Objective Evolutionary Algorithms (MOEA) to accelerate convergence speed and to produce a set of high quality solutions. Numerical results obtained from both optimization methods are compared in terms of computational expense and model quality. The benefits of using Hybrid-Game Strategies are clearly demonstrated.     

A Methodology for Constructing User-Oriented Requirements Specifications for Large-Scale Systems Using Electronic Hypermedia

requirements specifications are developed for large-scale systems, the final specification is usually an abstraction of the original requirements data into a text-based form that is often foreign to end-users. A method was developed for representing requirements through use of electronic multimedia. The resulting specification is capable of representing requirements and requirements data in a manner that is more representative of the real-world problem space than traditional specifications. This paper presents a method for incorporating multimedia exhibits, notably the results of rapid prototyping activities and animated simulation, into a requirements specification for large-scale C2I systems. To examine the effectiveness of the method, a multimedia requirements specification was developed based on an existing text specification for a real-world system. An experiment was also performed that showed the product of the methodology to be effective in increasing the understandability of the specification over that obtained from the text specification alone.     

Creation of a unit block library of architectures for use in assembled scaffold engineering

Guided tissue regeneration is gaining importance in the field of orthopaedic tissue engineering as need and technology permits the development of site-specific engineering approaches. Computer Aided Design (CAD) and Finite Element Analysis (FEA) hybridized with manufacturing techniques such as Solid Freeform Fabrication (SFF), is hypothesized to allow for virtual design, characterization, and production of scaffolds optimized for tissue replacement. However, a design scope this broad is not often realized due to limitations in preparing scaffolds both for biological functionality and mechanical longevity. To aid scientists in fabrication of a successful scaffold, we propose characterization and documentation of a library of micro-architectures, capable of being seamlessly merged according to the mechanical properties (stiffness, strength), flow perfusion characteristics, and porosity, determined by the scientist based on application and anatomic location. The methodology is discussed in the sphere of bone regeneration, and examples of catalogued shapes are presented. Similar principles may apply for other organs as well.     

Exact and Accurate Reanalysis of Structures for Geometrical Changes

A reanalysis approach for geometrical changes in structural systems is presented. The solution procedure is based on the combined approximations method, where the binomial series terms are used as basis vectors in reduced basis approximations. The calculations are based on results of a single exact analysis, calculation of derivatives is not required, and each reanalysis involves a small computational effort. The method is easy to implement, and can be used with general finite element programs. Exact solutions are obtained efficiently for low-rank modifications in the geometry. Accurate solutions are achieved in cases where the basis vectors come close to being linearly dependent. Such solutions are also achieved for nearly scaled geometries, when the angle between the two vectors representing the initial design and modified design is small. Numerical examples demonstrate the high accuracy achieved with a small number of basis vectors     

Error-based segmentation of cloud data for direct rapid prototyping

This paper proposes an error-based segmentation approach for direct rapid prototyping (RP) of random cloud data. The objective is to fully integrate reverse engineering and RP for rapid product development. By constructing an intermediate point-based curve model (IPCM), a layer-based RP model is directly generated from the cloud data and served as the input to the RP machine for fabrication. In this process, neither a surface model nor an STL file is generated. This is accomplished via three steps. First, the cloud data is adaptively subdivided into a set of regions according to a given subdivision error, and the data in each region is compressed by keeping the feature points (FPs) within the user-defined shape tolerance using a digital image based reduction method. Second, based on the FPs of each region, an IPCM is constructed, and RP layer contours are then directly extracted from the models. Finally, the RP layer contours are faired with a discrete curvature based fairing method and subsequently closed to generate the final layer-based RP model. This RP model can be directly submitted to the RP machine for prototype manufacturing. Two case studies are presented to illustrate the efficacy of the approach.     

Integration of CAD and boundary element analysis through subdivision methods

Subdivision methods have been mainly used in computer graphics. This paper extends their applications to mechanical design and boundary element analysis (BEA), and fulfills the seamless integration of CAD and BEA in the model and representation.Traditionally, geometric design and BEA are treated as separate modules requiring different representations and models, which include continuous parametric models and discrete models. Due to the incompatibility of the involved representations and models, the post-processing in geometric design or the pre-processing in BEA is essential. The transition from geometric design to BEA requires substantial effort and errors are inevitably introduced during the transition. In this paper, a framework of realizing the integration of CAD and BEA was first presented based on subdivision methods. A common model or a unified representation for geometric design and BEA was created with subdivision surfaces. For general 3D structures, automatic mesh generation for geometric design and BEA was fulfilled through subdivision methods. The seamless integration improves the accuracy of numerical analysis and shortens the cycle of geometric design and BEA.     

Surface roughness visualisation for rapid prototyping models

When considering the use of rapid prototyping (RP), there are many questions a designer might ask. One such question is “what build orientation should be used to minimise the adverse effects of surface roughness?” At present, this decision is often made in an intuitive way or sometimes overlooked completely. This paper describes a methodology and software implementation that provides the designer with a computer graphics based visualisation of RP model surface roughness. This enables the build orientation to be determined as a result of increased designer knowledge. The surface roughness values were obtained through an extensive empirical investigation of several RP techniques. These are used as the database for a visualisation algorithm that represents varying surface roughness of the RP model as colour shading within a CAD image. The nature of the empirical measurements is analysed and the functionality of the software algorithm is described. Examples are given that demonstrate the use and benefits of the methodology. Finally, conclusions are drawn as to the significance of the work and future research directions are outlined.     

An automatic method for controlling the centre of gravity of a model

In many applications the location of the centre of gravity of a mechanical part is an important factor that a designer must consider. If it is not in a desired location, a part might not work properly, e.g. unbalanced force might be generated in a rotational part. After a part is modeled, its centre of gravity cannot be altered unless its external shape or internal mass distribution is changed. However, the external shape is usually constrained by other design considerations. In this paper, an algorithm is proposed for controlling the centre of gravity of a hollowed part. Using this algorithm, the location of the centre of gravity of a part is controlled by changing its internal mass distribution.     

Classification and mass production technique for three-quarter shoe insoles using non-weight-bearing plantar shapes

We have developed a technique for the mass production and classification of three-quarter shoe insoles via a 3D anthropometric measurement of full-size non-weight-bearing plantar shapes. The plantar shapes of fifty 40-60-year-old adults from Taiwan were categorized and, in conjunction with commercially available flat or leisure shoe models, three-quarter shoe-insole models were generated using a CAD system. Applying a rapid prototype system, these models were then used to provide the parameters for manufacturing the shoe insoles. The insoles developed in this study have been classified into S, M and L types that offer user-friendly options for foot-care providers. We concluded that these insoles can mate tightly with the foot arch and disperse the pressure in the heel and forefoot over the foot arch. Thus, practically, the pressure difference over the plantar region can be minimised, and the user can experience comfort when wearing flat or leisure shoes.